The application of coatings to surfaces is known. For example, U.S. Pat. Nos. 4,073,967 and 4,084,021 disclose the application of abrasion-resistant coatings to surfaces by spin coating, dip coating, spray coating, and flow coating techniques. While these techniques have been successful when used to coat smooth surfaces, such as the optical surface of single vision spectacle lenses, they have not been entirely satisfactory. For example, such techniques result in a build-up of a coating material at the outer edge of the lens which causes optical aberrations. Such techniques are even less satisfactory when they are used to coat irregular surfaces, such as those present on multivision ophthalmic devices, particularly those made from plastic. Such devices generally have segments which project abruptly away from (e.g. project above or below) at least one major optical surface of the device. Coating solutions applied to these optical surfaces by spin, dip, spray, or flow techniques must flow around and over these segments. The resulting coating generally exhibits flow marks around the projection and is thick at the intersections of the segment and the optical surface. This intersection is referred to hereinafter as the segment line.
Vapor coating techniques may also be employed. However, the resulting coatings tend to be very thin, for example 0.5 micron thick, and consequently are not useful in providing significant abrasion resistance.
U.S. Pat. No. 4,081,478 discloses a molding method wherein parts are first cast in a mold after which the mold is opened to provide a space for the injection of a predetermined quantity of coating composition. The mold is closed to spread the coating composition over the surface of the cast part, the coating cured in the closed mold, and the coated part removed from the mold. This technique is complicated and does not provide good adhesion of the coating to the substrate surface.
In yet another technique a gel coating material is applied to the surface of a mold and allowed to partially cure. See U.S. Pat. No. 4,081,578 at col. 2, lines 15-22. A mixture of resin compound and glass fibers is applied to and rolled over the gel coat. The resulting composite structure is allowed to cure. The purpose of this technique is to fill in any defects on the surface of an article.
U.S. Pat. No. 4,338,269 discloses a technique for applying a coating to the surface of a molded article. In this technique a composition containing a pentaerythritol base polyacrylate or polymethacrylate and a cellulose ester or a vinyl chloride-vinyl acetate containing polymer is applied to a mold and fully cured by exposure to actinic radiation. Subsequently a polymerizable composition is charged to the mold and polymerized. Such compositions exhibit only minimal abrasion resistance and have not been found to provide optically clear coatings.
U.S. Pat. No. 3,968,305 discloses a shaped article and a method for applying a "mar-resistant" layer thereto. One method disclosed in this patent involves the steps of
first, applying to a mold a polymerizable material selected from PA1 second, polymerizing the polymerizable material to form an abrasion-resistant film on the mold; PA1 third, charging a monomer to the mold; and PA1 fourth, polymerizing the monomer.
(a) a compound having a total of at least three acryloxy and/or methacryloxy groups in the molecule which are linked with an aliphatic hydrocarbon residue having not more than 20 carbon atoms, PA2 (b) a monomer mixture comprising at least 20% by weight of said compound and at most 80% by weight of at least one other copolymerizable monomer, or PA2 (c) a partially polymerized product of said compound or said monomer mixture;
The article and method of the present invention do not require the formation of an abrasion-resistant film on the mold prior to introduction of the monomer. To the contrary such a technique would not work in the invention as is shown below.